Thousands of Greeks vented frustration at their economic lot as they marched in Athens to mark the anniversary of the bloody 1973 student uprising that helped topple the then-military junta.

Students, workers and pensioners held banners reading: "We won't become a generation of unemployment and fear," reflecting widespread fury at the leftist-led government which signed up to more austerity as part a third international bailout, despite its pre-election promises.

Hundreds of police guarded the peaceful march to the Embassy of the United States, which supported the seven-year military dictatorship that collapsed in 1974.

At the front of the procession, individuals held a blood-stained Greek flag which belonged to students engaged in the revolt which triggered an army crackdown.

Clashes between police and a separate, much smaller group broke out in the streets near the Athens Polytechnic University, where dozens are believed to have been killed when tanks smashed its gates in 1973.

The annual march often becomes a focal point for protests against government policies amid rising public anger at pension and wage cuts demanded by the European Union and International Monetary Fund in exchange for loans.

"We want the government to do a true redistribution of wealth and, at long last, tax the wealthy. Not just pass the burden of the crisis onto the poor," said Sotiris Vaporidis, 58, a pensioner.

A group of self-proclaimed anarchist protesters occupied one of the Polytechnic University's buildings: "We won't forget the fallen of the war waged against society," they said in a statement on the Internet, referring to the financial crisis.

Since 2009, the debt crisis has shrunk Greece's economy by about a quarter, putting thousands of Greeks out of work and shutting down businesses.

Many Greeks blame governments since the fall of the junta of driving the country to near-bankruptcy.

During a commemorative session of parliament earlier, Prime Minister Alexis Tsipras said he was optimistic Greece would emerge from crisis.

"Our government received a mandate to pull the country out of the crisis, with society standing upright, smashing this vicious circle of austerity ... to restore the wounded democracy in our country during the era of bailouts," Tsipras said.